二维加糙明渠流理论床面的确定方法

Determination of zero-plane displacement in two-dimensional roughened open channel flow

确定粗糙明渠流的理论床面对分析流速分布的特性具有学术价值。针对二维半圆柱体加糙床面,通过改变水深、流量和粗糙元间距,开展了一系列水槽实验研究。运用粒子图像测速技术进行流场测量,首先获取经时间和空间平均后的流速垂线分布资料,然后分析了理论床面位移随雷诺数等多种水力参数的变化关系。为能综合反映水深、粗糙元高度及其间距等参数的影响,应用水力半径概念,提出了新的特征长度。分析结果表明:相较于其他参数,该特征长度可以更好地描述理论床面位移的变化。

A series of laboratory experiments were carried out in an open channel with a semi-cylinder roughened bed.The velocity field was measured by a particle image velocimetry technique(PIV).The data were further used to compute the temporal and spatial averaged velocity profiles.The variations of zero-plane displacement with Reynolds number and other hydraulic parameters were analyzed.To consider the combined influence of flow depth,roughness height and roughness spacing,the concept of hydraulic radius was applied to develop a new characteristic length.The results show that the characteristic length is better than other parameters in the description of the variation of the zero-plane displacement.